K–S probability evaluated between the two populations of LGRBs in the BAT6ext (from Arcodia et al. (2016)) and the SBAT4, as a function of the applied cut in z. Red dots represent the median value of the obtained K–S probability distribution, while green dots are their logarithmic mean value. As the redshift range increases, the probability follows a decreasing trend. The two populations are likely drawn from the same distribution up to z ∼ 1.2, then the probability crosses a band (between the green dashed lines, corresponding to a probability of 1% to 10%) where the K–S test is ambiguous, and keeps decreasing. At z ∼ 1.4 the logarithmic mean of the K–S probability has dropped below the 1% threshold, and at z ∼ 1.8 also the median value indicates that the two populations are likely different.